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Abstract

We demonstrate a compact, wide-field, quantitative phase contrast microscope that does not require lenses for image formation. High-resolution images are retrieved from Fresnel diffraction patterns recorded at multiple wavelengths, combined with a robust iterative phase retrieval algorithm. Quantitative phase contrast images of living cultured neurons are obtained with a transverse resolution of <2μm. Our system is well suited for high-resolution live cell imaging and provides a compact, cost-effective alternative to full-sized phase-contrast microscopes.

Figures (3)

(a) Schematic of the all-fiber-based lensless imaging setup. Three fiber-coupled laser diodes are combined into a single fiber using 2×2 fiber beam splitters (BS1 and BS2). The fiber output beam propagates toward a sample, and a CCD camera records the diffraction pattern for each wavelength by turning the lasers on and off sequentially. (b) Schematic of the Fresnel diffraction geometry used in the microscope. The diverging beam from the SMF is transmitted through an object onto a CCD. The beam divergence introduces a magnification factor in the microscope. (c) Picture of the imaging setup, showing the fiber output, the CCD camera, and the dish containing a coverslip with cells.

(a) Diffraction pattern of a USAF1951 resolution test target at 785 nm wavelength (logarithmic intensity scale). (b) Overlay of three diffraction patterns of the same object (log scale), recorded at 685 nm (blue), 785 nm (green), and 940 nm (red). (c) Retrieved image after 30 iterations of the multiwavelength phase retrieval algorithm and backpropagation to the object plane. Two diffraction patterns at 685 and 785 nm are used as input. (d) Retrieved image after the same phase retrieval procedure, using three diffraction patterns (wavelengths 685, 785, and 940 nm) as input.

(a) Diffraction pattern (logarithmic intensity scale) of a sample of live neurons grown on astrocytes, recorded at 940 nm wavelength. (b) Reconstructed intensity image at the object plane, using diffraction patterns at three wavelengths. (c) Reconstructed phase image of the sample, clearly showing the neurons. The scale bar shows the measured phase shift in radians.